package com.yzm.util;

import java.nio.charset.Charset;

public class Base64Util {

	public static final Charset UTF_8 = Charset.forName("UTF-8");
	private static IBase64 delegate;

	private Base64Util() {
	}

	static {
		if (isPresent("java.util.Base64", Base64Util.class.getClassLoader())) {
			delegate = new Java8Base64();
		} else {
			delegate = new Java67Base64();
		}
	}

	/**
	 * 编码
	 * 
	 * @param value
	 *            byte数组
	 * @return {String}
	 */
	public static String encode(byte[] value) {
		return delegate.encode(value);
	}

	/**
	 * 编码
	 * 
	 * @param value
	 *            字符串
	 * @return {String}
	 */
	public static String encode(String value) {
		byte[] val = value.getBytes(UTF_8);
		return delegate.encode(val);
	}

	/**
	 * 编码
	 * 
	 * @param value
	 *            字符串
	 * @param charsetName
	 *            charSet
	 * @return {String}
	 */
	public static String encode(String value, String charsetName) {
		byte[] val = value.getBytes(Charset.forName(charsetName));
		return delegate.encode(val);
	}

	/**
	 * 解码
	 * 
	 * @param value
	 *            字符串
	 * @return {byte[]}
	 */
	public static byte[] decode(String value) {
		return delegate.decode(value);
	}

	/**
	 * 解码
	 * 
	 * @param value
	 *            字符串
	 * @return {String}
	 */
	public static String decodeToStr(String value) {
		byte[] decodedValue = delegate.decode(value);
		return new String(decodedValue, UTF_8);
	}

	/**
	 * 解码
	 * 
	 * @param value
	 *            字符串
	 * @param charsetName
	 *            字符集
	 * @return {String}
	 */
	public static String decodeToStr(String value, String charsetName) {
		byte[] decodedValue = delegate.decode(value);
		return new String(decodedValue, Charset.forName(charsetName));
	}

	private static boolean isPresent(String className, ClassLoader classLoader) {
		try {
			Class.forName(className, true, classLoader);
			return true;
		} catch (Throwable ex) {
			return false;
		}
	}

	static interface IBase64 {
		public String encode(byte[] value);

		public byte[] decode(String value);
	}

	static class Java8Base64 implements IBase64 {
		@Override
		public String encode(byte[] value) {
			return java.util.Base64.getEncoder().encodeToString(value);
		}

		@Override
		public byte[] decode(String value) {
			return java.util.Base64.getDecoder().decode(value);
		}
	}

	static class Java67Base64 implements IBase64 {
		public String encode(byte[] data) {
			return javax.xml.bind.DatatypeConverter.printBase64Binary(data);
		}

		public byte[] decode(String base64) {
			return javax.xml.bind.DatatypeConverter.parseBase64Binary(base64);
		}
	}

}
